Biodegradable resins begin to degrade in several weeks by actions of enzymes produced by microorganisms living in nature in a case where the biodegradable resins are placed in soil, sea waters, or inside the body of animals, and disappear during a period of about a year to several years. Therefore, in recent years, utilization of the resins is being remarked from the viewpoint of increased interests in environmental-friendliness.
For example, in Patent Publication 1, a resin composition having excellent water resistance and flexibility while maintaining transparency of a lactic acid-based polymer is obtained, by using a polyester-based plasticizer having a repeating unit of a dihydric alcohol, terminals of which are capped with a monobasic acid and/or a monohydric alcohol, the polyester-based plasticizer having a total of acid value and hydroxyl value of 40 or less.
In Patent Publication 2, it is reported that a resin composition having excellent flexibility and storage stability is obtained by melt-kneading a lactic acid-based polyester previously subjected to deactivation treatment of a polymerization catalyst with a chelating agent and/or an acidic phosphoric ester, with a plasticizer, and that a molded article having excellent heat resistance and solvent resistance is obtained by molding and crystallizing the composition.